<!DOCTYPE html>
<html lang="zh">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Dom1</title>
  <style>
    .red {
      background-color: red;
    }
  </style>
</head>

<body>
  示例
  <div>
    <div id="test">test</div>
  </div>

  <div id="test2">
    <span>1</span>
    <span>2</span>
    <span>3</span>
  </div>

  <div id="test3">
    <strong>p</strong>
    test3
  </div>

  <div id="test4">
    <p class="red"></p>
  </div>

  <div id="test5">
    <p class="red"></p>
  </div>

  <script src="dom.js"></script>
  <script src="main.js"></script>

</body>

</html>